Great people, pleasant office environment, many small perks such as getting to attend corporate sponsored events, decent benefits especially for singles (paid medical, very cheap dental and vision, 5% contribution to 401K even if you don't contribute). Some positions have work schedule flexibility (others don't).
Cons
The nonprofit branch is under a larger for-profit corporation, and overall IT'S A CORPORATION. We never know who will be walked out the door at 4:30 on a Friday afternoon. Some people seem to advance without going through the channels others have to swim.